Mitochondrial disease patients with novel ND4 12058A > C and ND1 m.3911A > G variations: implications for a role in the phenotype following a bioinformatic investigation.

Mitochondrial diseases include a wide group of clinically heterogeneous disorders caused by a dysfunction of the mitochondrial respiratory chain and can be related to mutations in nuclear or mitochondrial DNA genes. In the present report, we performed a whole mitochondrial genome screening in two patients with clinical features of mitochondrial diseases. Mutational analysis revealed the presence of two undescribed heteroplasmic mitochondrial variations, the m.3911A > G (E202G) variant in the MT-ND1 gene found in two patients (P1 and P2) and the m.12058A > C (E433D) pathogenic variant in the MT-ND4 gene present only in patient P2 who had a more severe phenotype. These two substitutions were predicted to be damaging by several bioinformatics tools and lead to amino acid changes in two conserved residues localized in two important functional domains of the mitochondrial subunits of complex I. Furthermore, the 3D modeling suggested that the two amino acid changes could therefore alter the structure of the two subunits and may decrease the stability and the function of complex I. The two described pathogenic variants found in patient P2 could act synergically and alter the complex I function by affecting the proton pumping processes and the energy production and then could explain the severe phenotype compared to patient P1 presenting only the E202G substitution in ND1.

Primary ciliary dyskinesia gene contribution in Tunisia: Identification of a major Mediterranean allele.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disease of motile cilia. Even though PCD is widely studied, North-African patients have been rarely explored. In this study, we aim at confirming the clinical diagnosis and explore the genetic spectrum of PCD in a cohort of Tunisian patients. Forty clinically diagnosed patients with PCD belonging to 34 families were recruited from Tunisian pediatric departments. In each proband, targeted capture PCD panel sequencing of the 40 PCD genes was performed. PCD panel sequencing identified bi-allelic mutations in 82% of the families in eight PCD genes. Remarkably, 23.5% of patients carried the same c.2190del CCDC39 mutation. Single nucleotide polymorphism profiling in six unrelated patients carrying this mutation has revealed a founder effect in North-African patients. This mutation is estimated to date back at least 1,400-1,750 years ago. The identification of this major allele allowed us to suggest a cost-effective genetic diagnostic strategy in North-African patients with PCD.

Mutations in aARS genes revealed by targeted next-generation sequencing in patients with mitochondrial diseases.

Mitochondrial diseases are a clinically heterogeneous group of multisystemic disorders that arise as a result of various mitochondrial dysfunctions. Autosomal recessive aARS deficiencies represent a rapidly growing group of severe rare inherited mitochondrial diseases, involving multiple organs, and currently without curative option. They might be related to defects of mitochondrial aminoacyl t-RNA synthetases (mtARS) that are ubiquitous enzymes involved in mitochondrial aminoacylation and the translation process. Here, using NGS analysis of 281 nuclear genes encoding mitochondrial proteins, we identified 4 variants in different mtARS in three patients from unrelated Tunisian families, with clinical features of mitochondrial disorders. Two homozygous variants were found in KARS (c.683C>T) and AARS2 (c.1150-4C>G), respectively in two patients, while two heterozygous variants in EARS2 (c.486-7C>G) and DARS2 (c.1456C>T) were concomitantly found in the third patient. Bio-informatics investigations predicted their pathogenicity and deleterious effects on pre-mRNA splicing and on protein stability. Thus, our results suggest that mtARS mutations are common in Tunisian patients with mitochondrial diseases.

Hemophagocytic Lymphohistiocytosis: A Rare Complication of an Ultrarare Lysosomal Storage Disease.

Hemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening hyperinflammatory condition that may be triggered by infections, autoimmune and immunologic disorders, malignancies, and metabolic diseases. Early and accurate diagnosis of HLH and its underlying cause is of paramount importance for proper management and prognosis. We report the case of a Tunisian 21-month-old girl who initially presented clinical features of HLH related to a lysosomal acid lipase deficiency. The genetic sequence analysis of the LIPA gene revealed a never described homozygous mutation c.966G>C (p.Gln322His). The parents were heterozygous for this mutation. Enzyme replacement therapy was not provided for the patient. She received etoposide, corticosteroids, and cyclosporine for the HLH. She is waiting for hematopoietic stem cell transplantation. To the best of our knowledge, this is the second Tunisian case of secondary HLH complicating lysosomal acid lipase deficiency related to a new homozygous mutation: c.966G>C (p.Gln322His).

Cytochrome C oxydase deficiency: SURF1 gene investigation in patients with Leigh syndrome.

Leigh syndrome (LS) is a rare progressive neurodegenerative disorder occurring in infancy. The most common clinical signs reported in LS are growth retardation, optic atrophy, ataxia, psychomotor retardation, dystonia, hypotonia, seizures and respiratory disorders. The paper reported a manifestation of 3 Tunisian patients presented with LS syndrome. The aim of this study is the MT[HYPHEN]ATP6 and SURF1 gene screening in Tunisian patients affected with classical Leigh syndrome and the computational investigation of the effect of detected mutations on its structure and functions by clinical and bioinformatics analyses. After clinical investigations, three Tunisian patients were tested for mutations in both MT-ATP6 and SURF1 genes by direct sequencing followed by in silico analyses to predict the effects of sequence variation. The result of mutational analysis revealed the absence of mitochondrial mutations in MT-ATP6 gene and the presence of a known homozygous splice site mutation c.516-517delAG in sibling patients added to the presence of a novel double het mutations in LS patient (c.752-18 A > C/c. c.751 + 16G > A). In silico analyses of theses intronic variations showed that it could alters splicing processes as well as SURF1 protein translation. Leigh syndrome (LS) is a rare progressive neurodegenerative disorder occurring in infancy. The most common clinical signs reported in LS are growth retardation, optic atrophy, ataxia, psychomotor retardation, dystonia, hypotonia, seizures and respiratory disorders. The paper reported a manifestation of 3 Tunisian patients presented with LS syndrome. The aim of this study is MT-ATP6 and SURF1 genes screening in Tunisian patients affected with classical Leigh syndrome and the computational investigation of the effect of detected mutations on its structure and functions. After clinical investigations, three Tunisian patients were tested for mutations in both MT-ATP6 and SURF1 genes by direct sequencing followed by in silico analysis to predict the effects of sequence variation. The result of mutational analysis revealed the absence of mitochondrial mutations in MT-ATP6 gene and the presence of a known homozygous splice site mutation c.516-517delAG in sibling patients added to the presence of a novel double het mutations in LS patient (c.752-18 A>C/ c.751+16G>A). In silico analysis of theses intronic vaiations showed that it could alters splicing processes as well as SURF1 protein translation.

A novel TBX1 missense mutation in patients with syndromic congenital heart defects.

Congenital heart defects represent a characteristic part of several genetic syndromes associated with chromosomal abnormalities such as 22q11.2 deletion syndrome; many genes located in this locus, mainly TBX1, are candidate genes for congenital heart defects. In our cohort of 27 subjects with congenital heart defect, both karyotype analysis and Fluorescence in situ hybridization (FISH) were performed. The TBX1 gene was sequenced in patients lacking chromosomal abnormalities. FISH analysis showed a de novo 22q11.2 deletion in two patients. The screening of TBX1 coding sequence identified a novel missense mutation c.569C > A (p.P190Q) in six unrelated patients and detected two associated known single nucleotide polymorphisms; the c.664C > T (rs2301558) in three patients and the c.420T > C (p.Phe140 Phe) (rs41298814) in one patient. Bioinformatic tools show that the novel missense mutation c.569C > A could modify the function and the stability of the TBX1 protein. The c.569C > A mutation was not found in 50 healthy controls. Ours results suggest a deleterious role of the c.569C > A mutation and strengthen the hypothesis that this mutation might be responsible for the same phenotype spectrum as the 22q11.2 deletion syndrome.

Clinical and genetic heterogeneity in familial steroid-sensitive nephrotic syndrome.

BACKGROUND: Familial steroid-sensitive nephrotic syndrome (SSNS) is a rare condition. The disease pathophysiology remains elusive. However, bi-allelic mutations in the EMP2 gene were identified, and specific variations in HLA-DQA1 were linked to a high risk of developing the disease. METHODS: Clinical data were analyzed in 59 SSNS families. EMP2 gene was sequenced in families with a potential autosomal recessive (AR) inheritance. Exome sequencing was performed in a subset of 13 families with potential AR inheritance. Two variations in HLA-DQA1 were genotyped in the whole cohort. RESULTS: Transmission was compatible with an AR (n = 33) or autosomal dominant (AD, n = 26) inheritance, assuming that familial SSNS is a monogenic trait. Clinical features did not differ between AR and AD groups. All patients, including primary (n = 7) and secondary steroid resistant nephrotic syndrone (SRNS), (n = 13) were sensitive to additional immunosuppressive therapy. Both HLA-DQA1 variations were found to be highly linked to the disease (OR = 4.34 and OR = 4.89; p < 0.001). Exome sequencing did not reveal any pathogenic mutation, neither did EMP2 sequencing. CONCLUSIONS: Taken together, these results highlight the clinical and genetic heterogeneity in familial SSNS. Clinical findings sustain an immune origin in all patients, whatever the initial steroid-sensitivity. The absence of a variant shared by two families and the HLA-DQA1 variation enrichments suggest a complex mode of inheritance.

Hypoparathyroidism in children: a study of eight cases.

BACKGROUND: Hypoparathyroidism is a rare pediatric endocrine disease, which is caused by low circulating levels of PTH or insensitivity to its action in the target tissues. AIM: To report the clinical and biochemical characteristics and theoutcome of 8 patients with hypoparathyroidism. METHODS: We analyzed retrospectively the results of clinical, biochemical, radiological findings of patients with hypoparathyroidism diagnosed in pediatric department of Hedi Chaker Hospital during the period 1994-2013. RESULTS: Eight patients (5 females and 3 males) were diagnosed with hypoparathyroidism during 20 years's period. The median age at the onset of first symptoms was 17,5 months (15 days- 5 years and 10 months). Seizures were the most commonly presenting symptom and were seen in seven cases. Eight patients were diagnosed with hypoparathyroidism (Di-Georges syndrome: one case, Sanjad Sakati syndrome: 3 case, kearns sayre syndrome: 1 case, autoimmune polyendocrinopathy candidiasis- ectodermal dystrophy: one case, idiopathic hypoparathyroidism: two cases. Conventional treatment was based on calcium and vitamin D analogs. The average of follow up was 5 years. Nephrocalcinosis was noted in two patients. The death occurred in five patients; it was related to hypocalcaemia in one patient. CONCLUSION: The diagnosis of hyperparathyroidism is easy; it's established on the association of hypocalcaemia and hyperphosphatemia. Etiologic approach is based on molecular findings. Vitamin D analog treatment of hypoparathyroidism in children involves the challenge, of adjusting treatment dosage to minimize both symptomatic hypocalcemia and asymptomatic, but potentially kidney-damaging, hypercalciuria causing nephrocalcinosis and renal insufficiency.

Frequent Infections, Hypotonia, and Anemia in a Breastfed Infant.

Vitamin B12 deficiency may be responsible of serious hematologic and neurodevelopmental abnormalities. We report the case of an infant who was hospitalized because of recurrent infections, failure to thrive, hypotonia, and weakness. He was 8 months old and had been exclusively breastfed. Blood cell count showed pancytopenia with megaloblastic bone marrow. The serum IgG concentration was low. Vitamin B12 level was very low and associated with increased urinary methylmalonic acid. Cobalamin deficiency was caused by mother's unrecognized pernicious anemia. Vitamin B12 supply led to rapid clinical and hematologic improvement.

Mitochondrial DNA triplication and punctual mutations in patients with mitochondrial neuromuscular disorders.

Mitochondrial diseases are a heterogeneous group of disorders caused by the impairment of the mitochondrial oxidative phosphorylation system which have been associated with various mutations of the mitochondrial DNA (mtDNA) and nuclear gene mutations. The clinical phenotypes are very diverse and the spectrum is still expanding. As brain and muscle are highly dependent on OXPHOS, consequently, neurological disorders and myopathy are common features of mtDNA mutations. Mutations in mtDNA can be classified into three categories: large-scale rearrangements, point mutations in tRNA or rRNA genes and point mutations in protein coding genes. In the present report, we screened mitochondrial genes of complex I, III, IV and V in 2 patients with mitochondrial neuromuscular disorders. The results showed the presence the pathogenic heteroplasmic m.9157G>A variation (A211T) in the MT-ATP6 gene in the first patient. We also reported the first case of triplication of 9 bp in the mitochondrial NC7 region in Africa and Tunisia, in association with the novel m.14924T>C in the MT-CYB gene in the second patient with mitochondrial neuromuscular disorder.

Mutational analysis in patients with neuromuscular disorders: Detection of mitochondrial deletion and double mutations in the MT-ATP6 gene.

Mitochondrial diseases encompass a wide variety of pathologies characterized by a dysfunction of the mitochondrial respiratory chain resulting in an energy deficiency. The respiratory chain consists of five multi-protein complexes providing coupling between nutrient oxidation and phosphorylation of ADP to ATP. In the present report, we studied mitochondrial genes of complex I, III, IV and V in 2 Tunisian patients with mitochondrial neuromuscular disorders. In the first patient, we detected the m.8392C>T variation (P136S) in the mitochondrial ATPase6 gene and the m.8527A>G transition at the junction MT-ATP6/MT-ATP8 which change the initiation codon AUG to GUG. The presence of these two variations in such an important gene could probably affect the ATP synthesis in the studied patient. In the second patient, we detected several known variations in addition to a mitochondrial deletion in the major arc of the mtDNA eliminating tRNA and respiratory chain protein genes. This deletion could be responsible of an inefficient translation leading to an inefficient mitochondrial protein synthesis in P2.

Mutational screening in patients with profound sensorineural hearing loss and neurodevelopmental delay: Description of a novel m.3861A > C mitochondrial mutation in the MT-ND1 gene.

Mitochondrial diseases caused by mitochondrial dysfunction are a clinically and genetically, heterogeneous group of disorders involving multiple organs, particularly tissues with high-energy demand. Hearing loss is a recognized symptom of a number of mitochondrial diseases and can result from neuronal or cochlear dysfunction. The tissue affected in this pathology is most probably the cochlear hair cells, which are essential for hearing function since they are responsible for maintaining the ionic gradients necessary for sound signal transduction. Several mitochondrial DNA mutations have been associated with hearing loss and since mitochondria are crucial for the cellular energy supply in many tissues, most of these mtDNA mutations affect several tissues and will cause syndromic hearing loss. In the present study, we described 2 patients with sensorineural hearing loss and neurodevelopmental delay in whom we tested mitochondrial genes described to be associated with syndromic hearing loss. One of these patients showed a novel heteroplasmic mitochondrial mutation m.3861A > C (W185C) which lead to a loss of stability of the ND1 protein since it created a new hydrogen bund between the unique created cystein C185 and the A182 residue. In the second patient, we detected two novel heteroplasmic variations m.12350C > A (T5N) and m.14351T > C (E108G) respectively in the MT-ND5 and the MT-ND6 genes. The TopPred II prediction for the E108G variation revealed a decrease of the hydrophobicity in the mutated MT-ND6.

Report of the Tunisian Registry of Primary Immunodeficiencies: 25-Years of Experience (1988-2012).

PURPOSE: Primary immunodeficiencies (PIDs) are a large group of diseases characterized by susceptibility to not only recurrent infections but also autoimmune diseases and malignancies. The aim of this study was to describe and analyze the distribution, clinical features and eventual outcome of PID among Tunisian patients. METHODS: We reviewed the record of 710 patients diagnosed with Primary Immunodeficiency Diseases (PIDs) from the registry of the Tunisian Referral Centre for PIDs over a 25-year period. RESULTS: The male-to-female ratio was 1.4. The median age at the onset of symptoms was 6 months and at the time of diagnosis 2 years. The estimated prevalence was 4.3 per 100,000 populations. The consanguinity rate was found in 58.2 % of families. According to the International Union of Immunological Societies classification, spectrums of PIDs were as follows: combined T-cell and B-cell immunodeficiency disorders account for the most common category (28.6 %), followed by congenital defects of phagocyte (25.4 %), other well-defined immunodeficiency syndromes (22.7 %), predominant antibody deficiency diseases (17.7 %), diseases of immune dysregulation (4.8 %), defect of innate immunity (0.4 %) and complement deficiencies (0.4 %). Recurrent infections, particularly lower airway infections (62.3 %), presented the most common manifestation of PID patients. The overall mortality rate was 34.5 %, mainly observed with combined immunodeficiencies. CONCLUSION: The distribution of PIDs was different from that reported in Western countries, with a particularly high proportion of Combined Immunodeficiencies and phagocyte defects in number and/or function. More is needed to improve PID diagnosis and treatment in our country.

Segregation of S292F TPO gene mutation in three large Tunisian families with thyroid dyshormonogenesis: evidence of a founder effect.

UNLABELLED: We aimed to identify causal mutation(s) in 13 patients with thyroid dyshormonogenesis (TD) from three consanguineous Tunisian families. A 12-year clinical follow-up showed phenotypic variability ranging from the presence to the absence of goiter, sensorineural deafness, and mental retardation. Genetic analysis using microsatellite markers within two candidate genes (TPO and PDS) gave evidence of linkage with the TPO gene. Sequencing of its 17 exons and their flanking intron-exon junctions revealed the previously described c.875C>T (p.S292F) mutation in homozygous state. No additional mutations were found in either a 900 bp of the TPO gene promoter or PDS gene. In silico analysis showed that p.S292F mutation might reduce the catalytic cavity of the TPO which would restrict access of a potential substrate to the catalytic pocket. Using 4SNPs and one microsatellite marker in the TPO gene, an associated haplotype: G-C-G-G-214 was found, giving evidence of a founder mutation. CONCLUSION: This is the first description of a TD causing mutation in Tunisia and thus may help to develop a genetic screening protocol for congenital hypothyroidism in the studied region. Although structural modeling suggested a pathogenic effect of this mutation, functional studies are needed. Additional causing and/or modifier genes, together with late diagnosis could explain the clinical variability observed in our patients.

Hemolytic anemia and metabolic acidosis: think about glutathione synthetase deficiency.

Glutathione synthetase deficiency (GSSD) is a rare disorder of glutathione metabolism with varying clinical severity. Patients may present with hemolytic anemia alone or together with acidosis and central nervous system impairment. Diagnosis is made by clinical presentation and detection of elevated concentrations of 5-oxoproline in urine and low glutathione synthetase activity in erythrocytes or cultured skin fibroblasts. The prognosis seems to depend on early diagnosis and treatment. We report a 4 months old Tunisian male infant who presented with severe metabolic acidosis with high anion gap and hemolytic anemia. High level of 5-oxoproline was detected in her urine and diagnosis of GSSD was made. Treatment consists of the correction of acidosis, blood transfusion, and supplementation with antioxidants. He died of severe metabolic acidosis and sepsis at the age of 15 months.

Neonatal purulent meningitis in southern Tunisia: Epidemiology, bacteriology, risk factors and prognosis.

OBJECTIVES: To study the epidemiological, clinical and bacteriological aspects and outcome of purulent neonatal meningitis (PNM). METHODOLOGY: Retrospective analysis of 55 cases of PNM hospitalized in the pediatric ward of Hedi Chaker Hospital from 1990 to 2012. Infants less than 29 days of age were included. The diagnosis was made on either the presence of bacteria in the cerebrospinal fluid (CSF) or the combination of pleocytosis >30 cells/mm(3), protein level >1.3 g/l and glucose level <2.2 mmol/l or CSF/blood glucose ratio <0.4. RESULTS: The male:female sex ratio was 1.75. One or more maternal risk factors for infection were found in 24 cases. The main symptoms were fever and poor feeding. Soluble antigen was positive in four cases and cultures had isolated the bacteria in 28 cases. The mortality rate was 40%. The sequelae rate in the survivors was 16.4%. CONCLUSION: This study emphasizes the severity of PNM with high rates of mortality and neurological sequelae.

Ataxia-telangiectasia in the south of Tunisia: A study of 11 cases.

BACKGROUND: Ataxia-telangiectasia (A-T) is a multisystem disorder characterized by progressive neurologic impairment, variable immunodeficiency, impaired organ maturation, X-ray hypersensitivity, oculocutaneous telangiectasia, and a predisposition to malignancy. AIM: We performed this study in order to describe clinical, immunological and molecular features of patients with AT followed in the south of Tunisia Methods: we performed a retrospective study (1996-2012) in the south of Tunisia about all cases of A-T in order to describe their clinical, immunological and molecular features. RESULTS: 11 cases of AT were found. The mean age at onset of symptoms was 20 months with extremes varying from 3 months to 4 years. The median time to diagnosis was 3.6 years (range: 0-12 years).The main clinical feature of cerebellar syndrome, ataxia, was present at diagnosis in 8 patients and occurred at mean ages of 2.8 years. Ocular telangiectasia occurred at a mean age of 3.9 years (extremes: 3 months and 7 years). Recurrent sino-pulmonary infections that affected 7 children occurred at the mean age of 4.3 years. The most common humoral immune abnormality was serum IgA deficiency. Lymphopenia was found in 7 cases and lack of CD4 T in 6 cases. Cytogenetic analyses showed chromosomal instability in all children and a translocation (7-14) in two patients. A molecular diagnosis established in 6 patients from 4 families showed 5 different mutations of ATM gene. After an average decline of 5 years and 6 months, 7 patients died of severe pulmonary infection. Among them, 3 were ATM mutated. CONCLUSION: Morbidity and mortality among patients with A- T are associated with ATM genotype.

Congenital heart disease in 37,294 births in Tunisia: birth prevalence and mortality rate.

AIM: To investigate the previously unknown birth incidence, treatment, and mortality of children with congenital heart disease in Tunisia. METHODS: We undertook a retrospective review of medical records of all patients who were born in 2010 and 2011, and were diagnosed in Sfax (Tunisia) with congenital heart defect. RESULTS: Among 37,294 births, 255 children were detected to have congenital heart disease, yielding a birth incidence of 6.8 per 1000. The most frequently occurring conditions were ventricular septal defects (31%), ostium secundum atrial septal defects (12.9%), and pulmonary valve abnormalities (12%). Coarctation of the aorta, tetralogy of Fallot, univentricular physiology, pulmonary atresia with ventricular septal defect, and transposition of the great arteries were found in 4.3%, 6.2%, 3.4%, 2.7%, and 2.7%, respectively. During the follow-up of 1 year, 23% of the children died. About three-quarters of those deaths happened before surgery. CONCLUSION: The present study is in line with the general estimates in the world. It has revealed a high case of mortality among the patients awaiting corrective surgery. These children need more facilities.

Hemolytic anemia and progressive neurologic impairment: think about triosephosphate isomerase deficiency.

We have reported the first Tunisian case of triosephosphate isomerase (TPI) deficiency in a 2-year-old girl. She was the first child of a nonconsanguineous couple. The disease included a neonatal onset of chronic hemolytic anemia, recurrent low-respiratory infections then progressive neurological involvement. The diagnosis was made after her death from the TPI values of her parents who exhibited intermediate enzyme deficiency. Molecular study of TPI genes showed that the father and the mother are heterozygous for Glu105Asp mutation. Pediatricians must be alert to the differential diagnosis in patients having hemolytic anemia and other concomitant manifestations.

[Cerebral imaging in epileptic children: study of 140 cases]. / Magerie cérébrale de l'épilepsie de lenfant. Etude de 140 observations.

BACKGROUND: Epilepsy is a chronic disease, often with an onset during childhood and characterized by spontaneous and recurrent seizures. It concerns 0.5-1% of children under 16 years of age. Being much more sensitive than computed tomography, magnetic resonance imaging is the technique of choice to identify an underlying cause. CT scan is used in emergency situations. AIM: To describe cerebral lesions in epilepetic children and to identify predicative factors of abnormal neuroimaging. METHODS: Authors present a retrospective descriptive study of Neuroimaging data of 140 epileptic children evaluated for a period from 2000-2007 in the paediatric departement of Sfax. RESULTS: The mean age at onset of seizures was 3 years. The sex ratio was 1.12. Psychomotor retardation was noted in 75 patients. The seizures were generalized in 75% of case. Neurological examination was abnormal in 73 cases (52%). The main indications for conducting a brain imaging were psychomotor retardation (65 cases) and focal onset seizures (25 cases). Anoxo-ischemic lesions were the most frequent cerebral anomalies followed by brain malformations. Predictors of pathological MRI were an age at onset of seizure <3 years, psychomotor retardation and abnormal neurological examination. CONCLUSION: The morphological imaging is recommended for recent seizures of the child with the exception of idiopathic epilepsies. MRI is the best imaging modality in exploration of epilepsy in this context.